Synchronization means for motion picture projector and tape recorder

ABSTRACT

A motion picture is synchronized with the sound reproduced by a tape recorder. The drive motor of the motion picture projector is controlled by a D.A converter which is provided with a digital input representing the difference in number of pulses between the accumulated number of synchronization pulses generated respectively by the motion picture projector and the tape recorder.

Waited States Patent [191 Numata et a1.

SYNCHRONIZATION MEANS FOR MOTION PICTURE PROJECTOR AND TAPE RECORDERinventors: Saburo Numata; Takashl Kagechika,

both of Ohmiya, Japan Assignee: Fuji Shashin Koki Kabushiki Kaisha,

Saitama-ken, Japan Filed: Dec. 7, 1971 Appl. No.: 205,621

Foreign Application Priority Data [45] July 3, 1973 [56] ReferencesCited UNITED STATES PATENTS 3,266,862 8/1966 Wagoner 352/ 12 3,441,3424/1969 Ball at al 352/17 Primary Examiner-Samuel S. Matthews AssistantExaminer-Michael L. Gellner Attorney-Fleit, Gripple & Jacobson 5 7]ABSTRACT spectively by the motion picture projector and the taperecorder.

4 Claims, 3 Drawing Figures Dec. 14, 1970 Japan 45/111586 US. Cl. 352/17Int. C1. G031) 31/04 Field of Search 352/12, l5, 16, 17, 352/19, 20

6 PULSE GENERATOR 8 16 10 I4 i SUM j PULSE AND gS DlFl-'.

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CON- VERTER PA-TENTEUJUL 3 ms DIFFERENTIAL SENSING AND CONTROLLINGCIRCUIT NUMBER OF PULSES BACKGROUND OF THE INVENTION This inventionrelates to means for synchronizing the operations of a motion pictureprojector and a tape recorder, and more particularly to means forobtaining synchronization between the picture projected by a motionpicture projector and the sound reproduced by a tape recorder by meansof pulses generated from the motion picture projector and pulsesgenerated from a recording tape.

When sound is reproduced concurrently with the projection of a pictureby using a tape recorder, it is necessary to synchronize the sound withthe projected motion picture. Without special synchronization means, thefeed of a film and the feed of a tape become asynchronous due tovariation in the film feeding speed or variation in the tape feedingspeed caused by the fluctuation of the power supply voltage, slippageoccurring in the tape feeding mechanism or stretching of the tape. Suchasynchronism in the projection of the motion picture results also whenthe power supply voltage to the motion picture camera or the taperecorder fluctuates at the time of simultaneous recording.

In order to obviate such inconvenience, it has been the practice toutilize synchronizing pulse signals at the time of projection whichpulse signals are previously recorded on the tape at the time ofphotographing.

Namely, the conventional practice has been to record the desired soundon the recording tape concurrently with the photographing pulse signalstaken from the film feeding mechanism of the motion picture camera, readthe pulse signals at the time of projection and compare the same withthe pulse signals generated by the film feeding mechanism of the motionpicture projector, determine the speed differential between the motionpicture projector and the tape recorder and control the rotation of thedriving motor of the motion picture projector or the tape recorder,thereby synchronizing the projected picture and the sound generated bythe tape recorder.

.For such synchronous control by means of pulses, it is essential thatthe start of the film of the motion picture projector and the start ofthe tape of the tape recorder be synchronized. Because, if the start ofthe film and the start of the tape are not synchronous, the pulsesgenerated by the motion picture projector and the pulses generated bythe tape recorder which are to be compared with said first pulses do notcorrespond to each other, and in result the synchronization meansperforms the synchronizing operation with a certain deviation betweenthe projected picture and the reproduced sound. This may be avoided bylengthening the pulse interval but too a long pulse interval isundesirable because it results in unstable synchronism between thepulses. For obtaining synchronization between the motion pictureprojector and the tape recorder by means of pulses, therefore, it hasbeen usually necessary to record a start signal on the film or tape inthe form of a notch, conductive element or magnetic signal, and startthe co-operating tape recorder or motion picture projector in responseto said start signal.

SUMMARY OF THE INVENTION The present invention provides novelsynchronization means which overcomes the above-described disadvantagesof the prior art.

The principal object of the present invention is to providesynchronization means for a motion picture projector and a taperecorder, by which the operations of the motion picture projector andtape recorder are automatically brought into synchronism even when thestart of said motion picture projector and the start of said taperecorder are asynchronous.

Another object of the invention is to provide synchronization means fora motion picture projector and a tape recorder, by which the operationsof the motion picture projector and tape recorder are automaticallybrought into synchronism even when asynchronism occurs between saidmotion picture projector and said tape recorder during the motionpicture projecting operation.

In order to attain these objects, the synchronization means of theinvention is so designed that the pulse signals from the motion pictureprojector and the pulse signals from the tape recorder are cumulativelycounted from the start and the counted numbers of the respective pulsesignals are compared with each other, and the driving means of themotion picture projector or tape recorder is controlled by thedifference between the number of said pulse signals.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view schematically showingan arrangement comprising the synchronization means of the invention;

FIG. 2 is a block diagram showing a synchronization control unit of thesynchronization means according to the invention; and

FIG. 3 is a graph showing the relationship between the pulse numberdifference and the controlling output voltage, for explaining thesynchronization control according to the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1, referencenumeral 1 designates a motion picture projector, 2 a film, 3 aprojection lens, 4 a shutter and 5 a driving motor, all of which are ofthe same construction and perform the same function as those inconventional motion picture projectors. Reference numeral 6 designates apulse generator of any known type which generates synchronizing pulsesin co-operation with the shutter 4 and is a switch to intermittently cutoff a current or an electromagnetic induction type pulse generatingunit. Reference numeral 7 designates a tape recorder, 8 a tape havingtwo or more tracks on which the sound corresponding to the picture takenby a motion picture camera and pulse signals generated from meanssimilar to the pulse generator 6 of the motion picture projector arealready recorded, 9 a magnetic head for reproducing the sound, 10 amagnetic head for sensing the pulse signals, 1 1 a differential sensingand controlling circuit including an addition and subtraction circuit tobe described later, 1' an amplifier and 13 a speaker.

Referring to FIG. 2, reference numerals 6, 8 and 10 respectivelydesignate the pulse generator, the tape and the pulse sensing head ofthe motion picture projector mentioned above, 14 a voltage amplifier, 15a pulse shaper, 16 the addition and subtraction circuit including aFlip-Flop circuit which perfroms addition and subtraction upon countingthe pulse signals from the motion picture projector and the pulsesignals from the tape, 17 a D-A converter for converting the digitaloutput from the addition and subtraction circuit 16 into an analogoutput, 18 and 19 a voltage amplifier and an output amplifierrespectively, and 5 the driving motor of the motion picture projectormentioned above. The aforesaid controlling circuit 11 is composed of theelements l4'- 19.

In the arrangement shown in FIGS. 1 and 2, the film 2 having picturesphotographed thereon is mounted on the motion picture projector 1, whilethe tape 8 having recorded thereon and the sound corresponding to thepictures of the film 2 and the synchronizing signals taken from themotion picture camera (not shown) is mounted on the tape recorder 7, andthen said tape recorder 7 is started. The sound recorded in the tape 8is reproduced by the speaker 13 through the head 9, and at the sametime, the start signal is picked up by the head 10. The start signalactuates a relay (not shown) of the motion picture projector 1 throughthe voltage amplifier 14, and concurrently turns on a projector lamp(not shown) and energizes the driving motor 5 of the motion pictureprojector 1 through the voltage amplifiers Thus, the projection of thepictures is started. The synchronizing pulses on the tape 8 are suppliedto the addition and subtraction circuit 16 through the head 10, thevoltage amplifier 14 and the pulse shaper 15 according to the feedingspeed of the tape recorder 7, while the pulses from the motion pictureprojector 1 are concurrently supplied from the pulse generator 6 to theaddition and subtraction circuit 16. The addition and subtractioncircuit 16 consists of a combination of a Flip-Flop circuit and aspecial gate circuit so as, for example, to add the pulse signals fromthe tape 8 and subtract the pulses from the motion picture projector 1.Therefore, when the output of the addition and subtraction circuit 16representative of the result of addition and subtraction of both pulsesis applied to the next D-A converter, the deviation between the motionpicture projector 1 and the tape recorder 8 from the start thereof istaken out as an output voltage representative of the pulse numberdifference as shown in FIG. 3. Namely, the output of the D-A converteris e when the feeding of the tape 8 advances ahead of the feeding of thefilm 2 by, for example, 2 pulses in terms of pulse number. This output eis applied to the output amplifier 19 through the voltage amplifier 18to accelerate the rotation of the driving motor 5 of the motion pictureprojector 1, whereby the picture catches up with the sound and thus thesound and the picture are synchronized. In this case, more pulses aregenerated from the motion picture projector 1 as the rpm. of the drivingmotor 5 increases, and when the result of addition and subtraction is 0in FIG. 3, the output voltage of the D-A converter is e which is theoutput voltage when the tape 8 and the motion picture projector l aremaintained in synchronism.

In the synchronous start of the motion picture projector 1 and the taperecorder 7 as described above, the operation of the tape recorder 7tends to run ahead even when the motion picture projector 1 and the taperecorder 7 are started concurrently, because the start of the drivingmotor of said motion picture projector is always delayed. However,addition and subtraction circuit 16 performs an addition of the pulsesgenerated by the advancing tape recorder 7 and memorizes the addednumber of pulses, and acts to accelerate the driving motor 5 through theD-A converter, so that the feeding speed of the motion picture projectorl readily catches up with the feeding speed of the tape recorder 7.Thus, the defect which has been apt to occur with the conventionalsynchronization means that the feeding speeds of the motion pictureprojector and the tape recorder are synchronized with a deviationbetween the picture and the sound, can be completely eliminated. It willbe obviously understood that, when the feeding speed of the motionpicture projector 1 happens to become faster than that of the taperecorder 7 for any reason during the picture projecting operation, theoutput voltage of the D-A converter 17 drops below e and accordingly thedriving motor 5 is decelerated, so that the number of pulses from themotion picture projector 1 becomes smaller than the number of pulsesfrom the tape recorder and the synchronization between the picture andthe sound is restored.

Although the present invention has been described with reference to theembodiment in which the rotation of the driving motor 5 of the motionpicture projector 1 is controlled in accordance with the operation ofthe tape recorder 7, it will be understood that it is easily possible toarrange for the synchronization to be obtained between the picture andthe sound by controlling the rotation of the driving motor of the taperecorder 7 in accordance with the operation of the motion pictureprojector 1.

What is claimed is:

1. In a system for creating synchronization between a motion picture andthe sound therefor by means of pulses generated from a motion pictureprojector and a tape recorder, a synchronization means comprising meansfor taking from themotion picture projector pulses the number of whichis proportional to the drive speed thereof, means for taking from thetape recorder, prerecorded pulses recorded on the tape at intervalscorresponding to those of said pulses generated by the projector,counting and comparing means for counting the accumulated number of eachtype of pulse, determining the difference in the number of each type ofpulses, and generating an output proportional to said difference innumber, and means for controlling the driving means of a projector ortape recorder according to the output of said counting and comparingmeans so as to make the number of both types of pulses equal.

2. A synchronization means as defined in claim 1 wherein said pulsecounting and comparing means comprises an addition and subtractioncircuit.

3. A synchronization means as defined in claim 2 wherein said pulsecounting and comparing means further comprises a digital to analogconverter for converting the digital output of said circuit into ananalog input for controlling the driving means of the projector or thetape recorder.

4. A synchronization means for synchronizing a motion picture and itssound track, comprising means for cumulatively counting and comparingthe number of pulses generated by a motion picture projector and a taperecorder, means for developing a control signal proportional to thedifference between the number of said pulses, and means for controllingthe film feeding speed of the motion picture projector according to saidcontrol signal, whereby the accumulated number of both types of pulsesis controlled to be equal.

* III '4

1. In a system for creating synchronization between a motion picture andthe sound therefor by means of pulses generated from a motion pictureprojector and a tape recorder, a synchronization means comprising meansfor taking from the motion picture projector pulses the number of whichis proportional to the drive speed thereof, means for taking from thetape recorder, prerecorded pulses recorded on the tape at intervalscorresponding to those of said pulses generated by the projector,counting and comparing means for counting the accumulated number of eachtype of pulse, determining the difference in the number of each type ofpulses, and generating an output proportional to said difference innumber, and means for controlling the driving means of a projector ortape recorder according to the output of said counting and comparingmeans so as to make the number of both types of pulses equal.
 2. Asynchronization means as defined in claim 1 wherein said pulse countingand comparing means comprises an addition and subtraction circuit.
 3. Asynchronization means as defined in claim 2 wherein said pulse countingand comparing means further comprises a digital to analog converter forconverting the digital output of said circuit into an analog input forcontrolling the driving means of the projector or the tape recorder. 4.A synchronization means for synchronizing a motion picture and its soundtrack, comprising means for cumulatively counting and comparing thenumber of pulses generated by a motion picture projector and a taperecorder, means for developing a control signal proportional to thedifference between the number of said pulses, and means for controllingthe film feeding speed of the motion picture projector according to saidcontrol signal, whereby the accumulated number of both types of pulsesis controlled to be equal.